Solves #338 - assertions for safe_t_test

[wwojciech]

Fixes #338

Checks

• (Have you updated the NEWS.md ?)
• (Have you added proper tests for new functions/features ?)
• (Have you added new functions to the pkgdown.yml ?)
• (Have you run document() on new functions ?)

[munoztd0]

Looks good to me, but why removing the NA logic and tests, did you talk with @iaugusty about it ?

[wwojciech]

Looks good to me, but why removing the NA logic and tests, did you talk with @iaugusty about it ?

@munoztd0 - You mean the assertions against NA in x and y? That is because: (1) computations on NAs do not make sense; and (2) the safe_t_test() computations should be safe, i.e. they should not silently remove any NAs.

I did not explicitly talk to Ilse about it, but if you look at the code where safe_t_test() is used by Ilse, the NAs are already removed. See here:

junco/R/a_summarize_aval_chg_diff.R

Lines 12 to 15 in e01232c

	x1 <- x1[!is.na(x1)]
	x2 <- x2[!is.na(x2)]
	ttest_stat <- safe_t_test(x1, x2, conf.level = control$conf_level)